Hyraxes are telling us something

In chapter 7 of my book, I take up the question of how to make and characterize animal models of autism, schizophrenia and depression. In the case of autism, one of the defining features is a loss or lack of communication, and the question is, how to test for this in potential rodent models of autism. I describe efforts in my laboratory and others to quantify verbal communication in mice by recording their ultrasonic vocalizations in a variety of social situations. We found that in our model of an autism risk factor, maternal infection or maternal immune activation, the offspring of such mothers display deficits in the number of vocalizations. These offspring also utilize a somewhat different set of syllables in their ultrasonic calls than normal mice. These results indicate that the offspring of immune activated mothers display altered verbal communication.

But other fascinating questions involve the content of the calls – we and others are trying to find out if individual mice have unique calls that can be used by other mice to identify them, and also, are calls learned during development? There was a report several years ago claiming that individual male mice do have unique calls, but this has yet to be replicated. One of the difficulties in this research is how to easily and objectively analyze the syntax – the order of the elements – of the vocalizations. In a recent paper from Israel, Kershenbaum and colleagues analyze the “syntactic structure and geographical dialects in the songs of male rock hyraxes”. The rock hyrax is a 3 kg, social mammal found in Africa and the Middle East, and the males produce long and complex songs that can last several minutes. The authors of this study suggest that these calls or songs carry information that identify the caller. The most interesting finding in this new work is that the structure or syntax of the calls is similar among males in nearby groups, but is different between groups that are widely separated; thus the term, “geographic dialects”. In theory, these dialects could be maintained by social learning in the group or by genetic inheritance. the authors argue that it is likely that “dispersing males carry song features from their natal group, which are then repeated and learned at the destination sites”. It would be very interesting to see if laboratory mice (and wild mice) can learn syntactic features from one another. Moreover, would mouse models of autism display differences in these abilities?

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